View Compilation Error

0_0_26604848_6941.cpp: In function 'int main()':
0_0_26604848_6941.cpp:8:22: error: expected ';' before ')' token
      for(a=1;a<=n,a++)
                      ^
0_0_26604848_6941.cpp:10:18: error: 'i' was not declared in this scope
          sum=sum+i;
                  ^